The present invention relates to a color picture tube grid apparatus and, more particularly, to a color picture tube grid apparatus having a color selection grid constituted by slit holes.
In a conventional color picture tube grid apparatus, as shown in FIG. 5, a pair of side frame portions 1 and 2, which are arranged to oppose each other at a predetermined distance, are supported by a pair of arm portions 3 and 4 at positions near the Bessel points of the side frame portions 1 and 2 so as to form a predetermined frame, and a mask 7 constituted by grid elements 5 having a predetermined tension distribution is stretched across the frame and is welded/supported thereon.
Since elongated slit holes 8 are formed between the grid elements 5, each grid element 5 is very narrow and arcuate and receives a tension to be susceptible to mechanical vibration and deformation. For this reason, when phosphors are to be formed on the panel surface, the grid elements are shaken by the vibration of an exposure base or the like. As a result, portions to be exposed are shifted, and the phosphors cannot be correctly formed on the panel surface.
It may be considered that exposure is performed after the above-mentioned vibration is attenuated almost completely. However, since it takes much time for the vibration to be completely attenuated, a deterioration in productively occurs. In addition, even in a product, if the grid elements 5 are shaken by an external shock or the like, an image is adversely affected.
In order to prevent the above vibration, at least one damper line 6 is used, as shown in FIG. 5. This damper line 6 is arranged to be almost perpendicular to the longitudinal direction of the grid elements 5. With the damper line 6, vibration can be quickly suppressed to prevent the shaking movement of the grid elements 5.
Although the use of a plurality of damper lines can prevent the vibration and deformation of the grid elements, the damper lines shield light from a light source in an exposing operation. As a result, no phosphors are formed on portions shaded with the damper lines or the phosphors on the portions become thinner than those on other portions, thus adversely affecting an image.